diff --git a/heracles/catalog/filters.py b/heracles/catalog/filters.py
index 7483bce..00f1966 100644
--- a/heracles/catalog/filters.py
+++ b/heracles/catalog/filters.py
@@ -60,7 +60,10 @@ def __call__(self, page):
 
 
 class FootprintFilter:
-    """Filter a catalogue using a footprint map."""
+    """Filter a catalogue using a footprint map.
+    This rempoves the pixels that are not in the footprint map.
+    Moreover, it removes the pixels which have NaN values in the
+    longitude and latitude columns."""
 
     def __init__(self, footprint, lon, lat):
         """Filter using the given footprint map and position columns."""
@@ -91,6 +94,9 @@ def __call__(self, page):
         from healpy import ang2pix
 
         lon, lat = self._lonlat
-        ipix = ang2pix(self._nside, page[lon], page[lat], lonlat=True)
+        _lon, _lat = page[lon], page[lat]
+        good_entry = np.isfinite(_lon) & np.isfinite(_lat)
+        _lon, _lat = _lon[good_entry], _lat[good_entry]
+        ipix = ang2pix(self._nside, _lon, _lat, lonlat=True)
         exclude = np.where(self._footprint[ipix] == 0)[0]
         page.delete(exclude)